There are some threads showing the frame of a sixties Trade Winds.
Here is one enthusiastic vintage Airstream rebuilder that has some photos of his 68, with and without the foam insulation. See post #30.
There have been significant changes since 61. I think yours was the first year of the Dura Torq axles, of which some were welded on.
I'll try to remember another one. I've seen pictures of frames, but I wonder if they have enough detail to help you. My rear bumper is welded to the frame rails. There is the infamous angle iron that the rear of the body bolts to. And the outriggers need to mirror the good side of your frame. Your body and C-channel dictate how the frame will be.
I didn't remove my shell, just replaced the rear 42" of subfloor under the bath. This is the best picture I could find of the rear of my frame. At least you can see the rear cross member.